Monitoring Patterns of North America's Migratory Birds along the northern coast of the Gulf of Mexico

Background

Migratory birds spend up to four months of the year in spring and fall migrations. Most of that time is spent at stopover sites replenishing fat and protein reserves for energetically demanding nocturnal flights. Species abundances are often exceptionally high in limited habitat at migration stopover sites. Many species that occupy different ranges during breeding or wintering occur together during migration along the northern coast of the Gulf of Mexico. Understanding the factors that affect the timing and condition of birds during migration can inform managers and scientists about the most important conservation priorities that may prevent future declines.

We are banding migrants in some of the first resting and refueling habitat for northward migrants after hundreds of miles of non-stop flight across the Gulf of Mexico. The Nature Conservancy's Clive Runnells Family Mad Island Marsh Preserve (Mad Island) in Matagorda County, Texas has several unique and rare habitats and is situated in the middle of the Central and Mississippi Migration Flyways. The Migratory Bird Research Group at the University of Southern Mississippi is concurrently banding birds in Johnson's Bayou, Louisiana. These sister sites are within the peak spring passage region for eastern North American migrants and, therefore, well situated to capture an abundance of many species from broad geographic regions.

Objectives

What is the timing, distribution and abundance of migrants at high density spring stopover sites along the northern coast of the Gulf of Mexico? How does winter habitat quality affect the condition and timing of migrating birds? Do birds migrating to breeding latitudes pass through stopover sites at the same times?
Events occurring prior to and during spring migration are likely to affect timing of arrival, access to high-quality breeding habitats, and ultimately reproduction and survival. Practically nothing is known about how wintering conditions affect the condition of birds along the migration route. We can only obtain such information while birds are actively migrating with information obtained from stable isotopic signatures of tissues, which allows us to know the birds' previous habitat use and geographic origins.

Are migratory birds carrying exotic tick species into the United Sates? Migratory birds may be playing an under-recognized role in facilitating invasions of Neotropical ticks and tick-borne pathogens into the United States.
Songbirds in Central and South America are known to host Neotropical ticks that carry a suite of pathogens potentially harmful to humans. Ticks typically attach to a host and feed for several days and during this time a migratory bird can move hundreds of kilometers including across the Gulf of Mexico into the United States. Recent work suggests millions of exotic ticks are likely moving into the Unites States each year and potentially carrying harmful pathogens with them. Yet, the frequency, origin and destination of ongoing Neotropical tick invasions into the United States have not been studied, in large part due to our inability to track the movement of birds that serve as their carriers.

In the course of conducting this research, we hope to increase awareness of the importance of the northern coast of the Gulf of Mexico to bird populations, and increase awareness of the phenomenon of bird migration, ecology, and conservation.

Progress

During 2012, we captured over 1,500 birds of nearly 80 species. During the spring of 2013, we captured 3,160 migrants of 84 species.

During 2013, we collected 66 ticks from 25 species of birds. These ticks have been molecularly identified and screened for pathogens. All individual nymphs and larval pools of ticks that we processed were confirmed molecularly to be one of seven species in the genus Amblyomma. Only two of these species are known to occur in the United States.

We have completed isotopic analysis (δ13C and δD) of the toenail and tail feather tissues collected at both sites from three species; Ovenbird, Wood Thrush, and American Redstart.

The Mad Island banding station has also had a significant impact on a growing number of students. During the spring of 2012, over 125 students from local schools visited the banding station and during the spring of 2013 almost 300 students visited. A number of the children told us that they would like to visit other natural places to see if they could catch more fiddler crabs, see how healthy the water was, and just see more wildlife—especially birds!